Periodic Mesoporous Organosilica Materials: Self‐Assembly of Carbamothioic Acid‐Bridged Organosilane Precursors

A new series of carbamothioic acid‐containing periodic mesoporous organosilica (PMO) materials has been synthesized by a direct cocondensation method, in which an organosilica precursor N,S‐bis[3‐(triethoxysilyl)propyl]carbamothioic acid (MI) is treated with tetraethyl orthosilicate (TEOS), and the nonionic surfactant Pluronic 123 (P123) is used as a template under acidic conditions in the presence of inorganic additives. Moreover, the synthesis of the PMO material consisting of the MI precursor without TEOS has been realized. These novel PMO materials have large surface areas, well‐ordered mesoporous structures, hollow fiberlike morphologies, and thick walls. They are also structurally well‐ordered with a high organosilica precursor content, and the carbamothioic acid groups are thermally stable up to 250 °C. Furthermore, the organosilica materials exhibit hydrothermal stability in basic solution.     

Responsive periodic mesoporous polydiacetylene/silica nanocomposites

Responsive PMO materials have been synthesized through co-assembly of bridged diacetylenic silsesquioxane and surfactant. The spatially defined polydiacetylenic component, mesoporous network, and the covalent proximity of polydiacetylene to silica endow the PMO with mechanical robustness, reversible chromatic responses, improved thermal stability, and faster responses to chemical stimuli. This research also provides an efficient molecular design and assembly paradigm to fabricate a family of conjugated optoelectronic materials, creating novel platforms for sensors, actuators, and other device applications.     

Adsorption behavior of nicotine on periodic mesoporous organosilicas

In this study, we focused on the adsorption of nicotine from aqueous solution such as water and simulated body fluids (SBFs), where SBF has ion concentrations approximately equal to those of human blood plasma. We prepared periodic mesoporous organosilica (PMO) materials as adsorbents from 4,4-bis(triethoxysilyl)biphenyl (BTES-biphenyl), 1,4-bis(triethoxysilyl)benzene (BTES-benzene) and bis[3-(trimethoxy silyl)propyl]amine (BTMS-amine) as precursors and investigated on their adsorption behavior of nicotine as a guest material under different solvent conditions. For this work, two different kinds of SBF, c-SBF and r-SBF, have been chosen, where c-SBF is a transitional SBF solution, and r-SBF is a modified SBF solution that is closer to human blood plasma. Adsorption of nicotine on PMOs has been characterized by a UV-Vis spectroscopy. The adsorption behavior was strongly dependent on the isoelectric point and hydrophobicity of the PMO as well as the hydrophobicity of nicotine.     

Hydrogen bonding-induced oxygen clusters and long-lived room temperature phosphorescence from amorphous polyols

Developing non-conjugated luminescent polymers (NCLPs) with fluorescence and long-lived room-temperature phosphorescence is of great significance for revealing the essence of NCLPs luminescence, which has gradually attracted the attention of researchers in recent years. Herein, polymethylol (PMO) and poly(3-butene-1,2-diol) (PBD) with polyhydroxy structures were prepared and their luminescence behaviors were investigated to reveal the clusteroluminescence (CL) mechanism. Compared with polyvinyl alcohol with non-luminescent behavior, PMO and PBD exhibit cyan-blue fluorescence with quantum yields of ca. 12% and green room-temperature phosphorescence with lifetimes of ca. 89 ms in the solid state. Both fluorescence and phosphorescence exhibit typical excitation-dependent CL behavior. Experimental and theoretical analyses show that the strong hydrogen-bonding interaction of PMO and PBD greatly promotes the formation of oxygen clusters and the through-space n-n interaction of oxygen atoms, enabling fluorescence and phosphorescence emission. Our results have enormous implications for understanding the CL mechanism of NCLPs and provide a new polymer design strategy for the rational design of novel NCLPs materials.     

Periodic Mesoporous Organosilicas with Helical and Concentric Circular Pore Architectures

This study systematically investigates periodic mesoporous organosilicas (PMOs) with controlled helical and concentric circular (CC) pore architectures prepared through a basic‐catalyzed sol–gel process by using an achiral cationic surfactant trimethyloctadecylammonium bromide (C₁₈TAB) as a structure‐directing agent, perfluorooctanoic acid (PFOA) as an additive, and 1,2‐bis(triethoxysilyl)ethane (BTEE) as a hybrid silica precursor. By increasing the weight ratio of PFOA/C₁₈TAB, a pore architecture transition of PMO materials from hexagonal‐arrayed, straight longitudinal channels to helical and CC mesostructures is achieved; such a transition has not been observed before in PMO materials. Our discovery is helpful in understanding the supramolecular cooperative assembly of hybrid materials and their structural and morphological evolution, which are important in the future applications of PMO materials.     

Heterogeneous organocatalysis at work: functionalization of hollow periodic mesoporous organosilica spheres with MacMillan catalyst

We report a new method for the synthesis of hollow-structured phenylene-bridged periodic mesoporous organosilica (PMO) spheres with a uniform particle size of 100-200 nm using α-Fe(2)O(3) as a hard template. Based on this method, the hollow-structured phenylene PMO could be easily functionalized with MacMillan catalyst (H-PhPMO-Mac) by a co-condensation process and a "click chemistry" post-modification. The synthesized H-PhPMO-Mac catalyst has been found to exhibit high catalytic activity (98% yield, 81% enantiomeric excess (ee) for endo and 81% ee for exo) in asymmetric Diels-Alder reactions with water as solvent. The catalyst could be reused for at least seven runs without a significant loss of catalytic activity. Our results have also indicated that hollow-structured PMO spheres exhibit higher catalytic efficiency than solid (non-hollow) PMO spheres, and that catalysts prepared by the co-condensation process and "click chemistry" post-modification exhibit higher catalytic efficiency than those prepared by a grafting method.     

Synthesis and characterization of organic-inorganic hybrid mesoporous silica materials with new templates

1-Hexadecane-3-methylimidazolium bromide and 1-hexadecane-2,3-dimethylimidazolium bromide were used as new templates for the syntheses of periodic mesoporous organosilica (PMO) materials; using these new templates, ethane-bridged PMO materials were successfully synthesized and characterized under basic conditions.     

Ordered Mesoporous Organosilica with Ionic‐Liquid Framework: An Efficient and Reusable Support for the Palladium‐Catalyzed Suzuki–Miyaura Coupling Reaction in Water

The preparation of a novel palladium‐supported periodic mesoporous organosilica based on alkylimidazolium ionic liquid (Pd@PMO‐IL) in which imidazoilium ionic liquid is uniformly distributed in the silica mesoporous framework is described. Both Pd@PMO‐IL and the parent PMO‐IL were characterized by N₂‐adsorption–desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), TEM, and solid‐state NMR spectroscopy. We have demonstrated that Pd@PMO‐IL is an efficient and reusable catalyst for the Suzuki–Miyaura coupling reaction of various types of iodo‐, bromo‐, and even deactivated aryl chlorides in water. It was also found that although the PMO‐IL nanostructure acts as reservoir for soluble Pd species, it can also operate as a nanoscaffold to recapture the Pd nanoparticles into the mesochannels thus preventing extensive agglomeration of Pd. This observation might be attributed to the isolated ionic liquid units that effectively control the reaction mechanism by preventing Pd agglomeration and releasing and recapturing Pd nanoparticles during the reaction process. The catalyst can be recovered and reused for at least four reaction cycles without significant loss of activity.     

Periodic Mesoporous Organosilica with Molecular‐Scale Ordering Self‐Assembled by Hydrogen Bonds

Nanoporous materials with functional frameworks have attracted attention because of their potential for various applications. Silica‐based mesoporous materials generally consist of amorphous frameworks, whereas a molecular‐scale lamellar ordering within the pore wall has been found for periodic mesoporous organosilicas (PMOs) prepared from bridged organosilane precursors. Formation of a “crystal‐like” framework has been expected to significantly change the physical and chemical properties of PMOs. However, until now, there has been no report on other crystal‐like arrangements. Here, we report a new molecular‐scale ordering induced for a PMO. Our strategy is to form pore walls from precursors exhibiting directional H‐bonding interaction. We demonstrate that the H‐bonded organosilica columns are hexagonally packed within the pore walls. We also show that the H‐bonded pore walls can stably accommodate H‐bonding guest molecules, which represents a new method of modifying the PMO framework.     

Hierarchical porous silica materials with a trimodal pore system using surfactant templates

Porous silica exhibiting a hierarchically ordered trimodal pore system with a well-defined reverse opal microstructure and bimodal mesoporosity in the walls has been prepared by using polystyrene latex spheres, a novel block copolymer and an ionic liquid surfactant as templates. The resulting materials exhibit hierarchical order at three length scales (small mesopores: 2-3 nm; large mesopores: 11-12 nm; macropores: 360 nm).     

Syntheses, properties and applications of periodic mesoporous organosilicas prepared from bridged organosilane precursors

Periodic mesoporous organosilicas (PMOs) prepared by surfactant-directed polycondensation of bridged organosilane precursors are promising for a variety of next-generation functional materials, because their large surface areas, well-defined nanoporous structures and the structural diversity of organosilica frameworks are advantageous for functionalization. This critical review highlights the unique structural features of PMOs and their expanding potential applications. Since the early reports of PMOs in 1999, various synthetic approaches, including the selection of hydrolytic reaction conditions, development of new precursor compounds, design of templates and the use of co-condensation or grafting techniques, have enabled the hierarchical structural control of PMOs from molecular- and meso-scale structures to macroscopic morphology. The introduction of functional organic units, such as highly fluorescent π-conjugates and electroactive species, into the PMO framework has opened a new path for the development of fluorescent systems, sensors, charge-transporting materials and solid-state catalysts. Moreover, a combinational materials design approach to the organosilica frameworks, pore wall surfaces and internal parts of mesopores has led to novel luminescent and photocatalytic systems. Their advanced functions have been realized by energy and electron transfer from framework organics to guest molecules or catalytic centers. PMOs, in which the precise design of hierarchical structures and construction of multi-component systems are practicable, have a significant future in a new field of functional materials (93 references).     

Site‐Selective Functionalization of Periodic Mesoporous Organosilica (PMO) with Macrocyclic Host for Specific and Reversible Recognition of Heavy Metal

A novel kind of macrocyclic‐host‐functionalized periodic mesoporous organosilica (PMO) with excellent and reversible recognition of Pb^II was developed. The macrocyclic host molecule cis‐dicyclohexano[18]crown‐6, with strong affinity to Pb^II, was carefully modified as a bridged precursor to build the PMO material. To break down the limit of the functionalization degree for PMOs incorporated with large‐sized moieties, a site‐selective post‐functionalization method was proposed to further decorate the external surface of the PMO material. The selective recognition ability of the upgraded PMO material towards Pb^II was remarkably enhanced without destroying the mesoporous ordering. Solid‐state ¹³C and ²⁹Si NMR spectroscopy, X‐ray photoelectron spectroscopy (XPS), XRD, TEM, and nitrogen adsorption–desorption isotherm measurements were utilized for a full characterization of the structure, micromorphology, and surface properties. Reversible binding of Pb^II was realized in the binding–elution cycle experiments. The mechanism of the supramolecular interaction between the macrocyclic host and metal ion was discussed. The synthetic strategy can be considered a general way to optimize the properties of PMOs as binding materials for practical use while preserving the mesostructure.     

Dissolution of cellulose in ionic liquids as a way to obtain test materials for metal-ion detection

Cellulose films containing entrapped analytical reagents suitable for metal-ion detection are produced by joint dissolution of cellulose and the reagents in ionic liquids then precipitation with water. The conditions of preparation of these test materials have been optimized and their properties have been studied. The film obtained by use of the ionic liquid 1-butyl-3-methylimidazolium chloride and 1-(2-pyridylazo)-2-naphthol has been used for colorimetric determination of divalent zinc, manganese, and nickel with detection limits at the 10⁻⁶ mol L⁻¹ level.     

微扰分子轨道法在有机化学中的应用

经Dewar, Hoffmann, Epiotis, Houk, Wolfe和Kost等理论化学家的努力,PMO理论已经成为研究影响分子构型、构象和(立体专一性和区域专一性)反应产物的结构因素的一个有效的手段。Epiotis的非键轨道作用理论已经使有机化学家认识到, 一个拥挤的构象或过渡态不一定是一个能量上不利的状态。π轨道作用的分析表明, 共轭基团间的作用在本质上是相斥的, 全平面构象不是共轭效应最大的构象。WSW-like法不仅为定量PMO法提供了一组完整的、具有正确集据数的轨道基组, 而且它还成功地将轨道作用能转化为原子作用能。     

聚离子液体材料在分离科学中的研究进展

离子液体作为新型离子化试剂,具有诸多优越的物理化学性质,比如:良好的溶解性、导电性、热稳定性、生物相容性及低蒸气压和不易燃等特点,近年来在分析化学领域得到广泛关注。聚离子液体材料结合了离子液体和聚合物的双重性质,已经成为分离科学研究的前沿领域。本文详细讨论了离子液体与目标物之间的多种作用机制,比如亲/疏水作用、氢键作用、离子交换、π - π 堆积及静电吸附作用等等,总结了聚离子液体材料在固相萃取、液相色谱、气相色谱、毛细管电泳及毛细管电色谱等领域的研究进展;最后,对聚离子液体材料的发展前景进行了展望。     

Novel imidazolium chiral ionic liquids that contain a urea functionality

Nine chiral room temperature ionic liquids (RTILs), which contain a chiral moiety and a urea functionality bonded to a imidazolium ring, have been designed and synthesized. The synthesis of these ionic liquids is concise and practical due to the commercial availability of the starting materials. These novel RTILs were readily prepared from 1-(3-aminopropyl)imidazole and amino acid ester derived isocyanates. We envision that these new chiral RTILs can serve as effective reaction media as well as chiral catalysts, which are presently being investigated in our laboratory.     

Periodic Mesoporous Organosilica Nanoparticles with Controlled Morphologies and High Drug/Dye Loadings for Multicargo Delivery in Cancer Cells

Despite the worldwide interest generated by periodic mesoporous organosilica (PMO) bulk materials, the design of PMO nanomaterials with controlled morphology remains largely unexplored and their properties unknown. In this work, we describe the first study of PMO nanoparticles (NPs) based on meta‐phenylene bridges, and we conducted a comparative structure–property relationship investigation with para‐phenylene‐bridged PMO NPs. Our findings indicate that the change of the isomer drastically affects the structure, morphology, size, porosity and thermal stability of PMO materials. We observed a much higher porosity and thermal stability of the para‐based PMO which was likely due to a higher molecular periodicity. Additionally, the para isomer could generate multipodal NPs at very low stirring speed and upon this discovery we designed a phenylene–ethylene bridged PMO with a controlled Janus morphology. Unprecedentedly high payloads could be obtained from 40 to 110 wt % regardless of the organic bridge of PMOs. Finally, we demonstrate for the first time the co‐delivery of two cargos by PMO NPs. Importantly, the cargo stability in PMOs did not require the capping of the pores, unlike pure silica, and the delivery could be autonomously triggered in cancer cells by acidic pH with nearly 70 % cell killing.     

Functional Poly(ionic liquid) Porous Membranes: From Fabrications to Advanced Applications†

Polyelectrolyte porous membranes (PPMs) belong to the most interesting classes of materials, because the synergy of tunable pore sizes and charge nature of polyelectrolyte endow them with wide-ranging practical applications. However, owing to the water solubility and ionic nature of the polyelectrolytes, traditional polyelectrolytes are difficult to use in scalable preparation of high-quality PPMs through the well-developed industrial methods. Poly(ionic liquid)s (PIL) are a subclass of functional polyelectrolytes bearing ionic liquid groups in their repeating unites, inheriting the advantages of ionic liquids (ILs) and macromolecular architecture features. In recent years, along with rapid development of PIL materials chemistry, considerable and significant developments involving the novel preparation methods, and structure-property-function relationships of PPMs have been made. In this review, we highlight the latest discovery and proceedings of PPMs, particularly the advancements in how to tailor structures and properties of PPMs by rational structure design of PILs. The formation mechanisms of various PPMs were also discussed in detail from the viewpoint of PILs molecular structures. A future perspective of the challenges and promising potential of PPMs is cast on the basis of these achievements. We expect that these analyses and deductions will be useful for the design of useful PPMs and serve as a source of inspiration for the design of future multifunctional PPMs.      

A Zinc Phthalocyanine Based Periodic Mesoporous Organosilica Exhibiting Charge Transfer to Fullerenes

Periodic mesoporous organosilica (PMO) materials offer a strategy to position molecular semiconductors within a highly defined, porous network. We developed thin films of a new semiconducting zinc phthalocyanine‐bridged PMO exhibiting a face‐centered orthorhombic pore structure with an average pore diameter of 11 nm. The exceptional degree of order achieved with this PMO enabled us to create thin films consisting of a single porous domain throughout their entire thickness, thus providing maximal accessibility for subsequent incorporation of a complementary phase. The phthalocyanine building blocks inside the pore walls were found to be well‐aggregated, enabling electronic conductivity and extending the light‐harvesting capabilities to the near IR region. Ordered 3D heterojunctions capable of promoting photo‐induced charge transfer were constructed by impregnation of the PMO with a fullerene derivative. When integrated into a photovoltaic device, the infiltrated PMO is capable of producing a high open‐circuit voltage and a considerable photocurrent, which represents a significant step towards potential applications of PMOs in optoelectronics.     

Synthesis and characterization of periodic mesoporous organosilicas from bridged organosilanes in the presence of mixed salts

A simple but effective synthetic pathway to periodic mesoporous organosilicas (PMOs) has been put forward in this article. The novelty of the present preparative route lies in that, for specific examples, highly ordered ethane- and benzenesilica PMOs can be facilely prepared in the presence of an inorganic salt pair within a wide compositional range, where no addition of mineral acids was necessary. Most of interest is that crystal-like pore walls were observed for the large-pore benzenesilica PMO promoted by this novel system, which has rarely been reported for copolymer-assembled organosilicas, even though the degree of molecular order is not as perfect as those benzenesilicas prepared under basic conditions utilizing cationic surfactants as template. Characterization results based on a series of techniques indicated that both inorganic salts are important for the assembly of ordered mesostructures under the present system, and a plausible formation mechanism deduced from the “salt-assisted” concept as previously reported for mesoporous nonsiliceous materials was discussed.